The Symphonium Helios is 8.5Ω at 83.3 dB/mW; the Symphonium Meteor is 9.7Ω at 90.9 dB/mW. This page covers what they ask of an amplifier, not how they sound.
The Helios needs 7.6 dB more than the Meteor to reach the same loudness — 47 mW against 8.1 mW.
| Specification | Helios | Meteor |
|---|---|---|
| Impedance | 8.5 Ω | 9.7 Ω |
| Sensitivity | 83.3 dB/mW | 90.9 dB/mW |
| Sensitivity (voltage) | 104.0 dB/V | 111.0 dB/V |
| Power for 100 dB | 47 mW | 8.1 mW |
| Voltage for 100 dB | 0.63 V | 0.28 V |
| Current for 100 dB | 74.2 mA | 28.9 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 1.06 Ω | 1.21 Ω |
| Sources that reach 100 dB out of 280 | 179 | 271 |
92 of the 280 sources have the power for the Meteor but not for the Helios — Apple USB-C dongle (US), Generic CX31993 dongles, JadeAudio JA11, 89 more.
4 sources are low enough in output impedance for the Meteor under the one-eighth rule but not for the Helios (FiiO K11, FiiO BTR7, FiiO Q7, 1 more).
179 of the 280 sources here reach 100 dB on both.
The Helios is more demanding than 98% of the 567 non-electrostatic models in this database; the Meteor than 71%.
| dB SPL | Helios power | Helios voltage | Meteor power | Meteor voltage |
|---|---|---|---|---|
| 80 | 0.47 mW | 63 mV | 0.08 mW | 28 mV |
| 85 | 1.5 mW | 0.11 V | 0.26 mW | 50 mV |
| 90 | 4.7 mW | 0.20 V | 0.81 mW | 89 mV |
| 95 | 15 mW | 0.35 V | 2.6 mW | 0.16 V |
| 100 | 47 mW | 0.63 V | 8.1 mW | 0.28 V |
| 105 | 148 mW | 1.12 V | 26 mW | 0.50 V |
| Source | Price | Headroom, Helios | Headroom, Meteor | Output impedance | Noise |
|---|---|---|---|---|---|
| FiiO KA11 | $29 | 4.4 dB | 12.6 dB | 0.7 Ω | 1.7 µV |
| FiiO BTR13 | $59 | 1.3 dB | 9.5 dB | 0.6 Ω | 1.0 µV |
| FiiO KA3 | $79 | 1.3 dB | 9.5 dB | 0.5 Ω | 1.7 µV |
Of the 280 sources here, 179 reach 100 dB on both. 60 of them also publish an output impedance low enough for both under the one-eighth rule and a noise figure that stays below the audible-hiss threshold with both.
The cheapest of the 60 is the FiiO KA11, at $29. It leaves 4.4 dB of headroom on the Helios and 12.6 dB on the Meteor, its output impedance is 0.7 Ω against a one-eighth limit of 1.06 Ω and 1.21 Ω, and its noise figure puts the hiss floor 31 dB and 24 dB below the 20 dB SPL this site treats as the point where a quiet room stops hiding it.
| Model | As printed | Tolerance | Standard |
|---|---|---|---|
| Helios | 12Hz - 24kHz, ± 2 dB | ±2 dB | not printed |
| Meteor | 12Hz - 21kHz, ± 3 dB | ±3 dB | not printed |
Symphonium prints 12Hz - 24kHz, ± 2 dB for the Helios and 12Hz - 21kHz, ± 3 dB for the Meteor.
Both sheets print a tolerance, which is rare enough to be worth pointing at: only 58 of the 490 models with a printed range do. These two ranges can be set against each other, because each of them says how far down the response is allowed to be at the ends.
Not a measurement; maker by maker.
Both have a page of their own. In full: Symphonium Helios and Symphonium Meteor. Every figure on this page comes from what Symphonium published, or is derived from it — what that maker publishes, counted.